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Combustion of Glycerine for Combined Heat
And Power Systems in Biodiesel Processing Facilities
By Tom Epp
ii
Combustion of Glycerine for Combined HeatCombustion of Glycerine for Combined HeatCombustion of Glycerine for Combined HeatCombustion of Glycerine for Combined Heat
And Power Systems in Biodiesel Processing FacilitiesAnd Power Systems in Biodiesel Processing FacilitiesAnd Power Systems in Biodiesel Processing FacilitiesAnd Power Systems in Biodiesel Processing Facilities
A thesis submitted in conformity withthe requirements for the degree of
BACHELOR OF SCIENCE (MECH. ENG.) at the University of Manitoba
Supervisor: Dr. Eric Bibeau
Department of Mechanical and Manufacturing EngineeringDepartment of Mechanical and Manufacturing EngineeringDepartment of Mechanical and Manufacturing EngineeringDepartment of Mechanical and Manufacturing Engineering
Combustion of Glycerine for Combined HeatCombustion of Glycerine for Combined HeatCombustion of Glycerine for Combined HeatCombustion of Glycerine for Combined Heat
And Power Systems in Biodiesel Processing FacilitiesAnd Power Systems in Biodiesel Processing FacilitiesAnd Power Systems in Biodiesel Processing FacilitiesAnd Power Systems in Biodiesel Processing Facilities
Composed by Tom Epp
A thesis submitted in conformity with the requirements for the degree of
BACHELOR OF SCIENCE (MECH. ENG.) at the University of Manitoba
Supervisor: Dr. Eric Bibeau
Department of Mechanical and Manufacturing EngineeringDepartment of Mechanical and Manufacturing EngineeringDepartment of Mechanical and Manufacturing EngineeringDepartment of Mechanical and Manufacturing EngineeringUniversity of ManitobaUniversity of ManitobaUniversity of ManitobaUniversity of Manitoba
2008200820082008
And Power Systems in Biodiesel Processing FacilitiesAnd Power Systems in Biodiesel Processing FacilitiesAnd Power Systems in Biodiesel Processing FacilitiesAnd Power Systems in Biodiesel Processing Facilities
Department of Mechanical and Manufacturing EngineeringDepartment of Mechanical and Manufacturing EngineeringDepartment of Mechanical and Manufacturing EngineeringDepartment of Mechanical and Manufacturing Engineering
ii
ABSTRACT
Biodiesel processing facilities are coming online all over the world, companies offer a wide range
of turnkey style plants which vary from the process type to the raw materials used. What remains
common to these plants is both the product and the waste generation. Specifically, the waste type
glycerine which can be upwards of 10% of the sellable product. This represents a hurdle for utilities, as
global demand for glycerine waste is low and it must be further processed before dumping. The
solution must be a two pronged approach: It must be economically attractive to utilities while at the
same time minimize GHG emissions. With natural gas and electrical costs representing the largest chunk
of production costs, investment in technologies which burn glycerine for steam and energy generation
will subsidize process and load consumption while mitigating waste issues.
iii
ACKNOWLEDGMENT
I would like thank
Dr. Eric Bibeau P.Eng
Ken Drysdale P.Eng
Brent Wall P.Eng
All of whom contributed and offered unwavering support
iv
TABLE OF CONTENTS Page
ABSTRACT ...................................................................................................................................................... ii
ACKNOWLEDGMENT .................................................................................................................................... iii
TABLE OF CONTENTS .................................................................................................................................... iv
List of Figures ............................................................................................................................................... vi
List of Tables ............................................................................................................................................... vii
Nomenclature ............................................................................................................................................ viii
1.0 Introduction ............................................................................................................................................ 1
1.1 Background ......................................................................................................................................... 1
1.2 Concept ............................................................................................................................................... 1
1.3 Scope of work...................................................................................................................................... 2
2.0 Combustibility and Burner design ........................................................................................................... 3
2.1 Fuel Characteristics ............................................................................................................................. 3
2.2 Babington Burner ................................................................................................................................ 4
2.2.1 Process Heating only .................................................................................................................... 6
2.3 Oil Burners for Electrical Generation .................................................................................................. 7
2.4 Boilers ................................................................................................................................................. 8
3.0 Steam generation for process heat and Thermodynamic Cycles ........................................................... 9
3.1 Modeling the Rankine Cycle ............................................................................................................... 9
3.2 AHU Supplemental Heating .............................................................................................................. 10
4.0 Steam Generation for Electricity .......................................................................................................... 12
4.1 Rankine Cycle optimization ............................................................................................................... 12
5.0 Environmental Impact ........................................................................................................................... 14
5.1 Photosynthesis and Sequestered Carbon ......................................................................................... 14
5.2 Carbon Dioxide Emissions ................................................................................................................. 15
6.0 Economics ............................................................................................................................................. 17
6.1 Biodiesel Economics .......................................................................................................................... 17
6.2 Glycerine Economics ......................................................................................................................... 18
v
6.3 Plant expansion ................................................................................................................................. 18
6.4 Plant Case Studies ............................................................................................................................. 22
6.5 Babington Burner Economics ............................................................................................................ 24
7.0 Discussion .............................................................................................................................................. 26
7.1 General Discussion ............................................................................................................................ 26
7.2 Errors ................................................................................................................................................. 26
8.0 Conclusion ............................................................................................................................................. 28
References .................................................................................................................................................. 29
Appendix A .................................................................................................................................................. 31
Appendix B .................................................................................................................................................. 32
Appendix C .................................................................................................................................................. 35
vi
List of Figures
Figure 1: Viscosity of Glycerine ..................................................................................................................... 3
Figure 2: Airtronic Babington Burner ............................................................................................................ 5
Figure 3: Babington Program ........................................................................................................................ 6
Figure 4: Wall Tube Boiler ............................................................................................................................. 8
Figure 5: Rankine Cycle ............................................................................................................................... 10
Figure 6: Photosynthesis Cycle ................................................................................................................... 14
Figure 7: Carbon Cycle ............................................................................................................................... 14
Figure 8: Biodiesel Distribution Worldwide ............................................................................................... 17
Figure 9: 5 year EAC study .......................................................................................................................... 23
Figure 10: 10 year EAC study ...................................................................................................................... 23
Figure 11: 30 year EAC study ...................................................................................................................... 24
vii
List of Tables
Table 1: Fuel Comparisons ............................................................................................................................ 4
Table 2: Process Heat only ............................................................................................................................ 7
Table 3: Burner Fuel Rates ............................................................................................................................ 7
Table 4: Model Properties ............................................................................................................................ 9
Table 5: Glycerine Capacity ......................................................................................................................... 13
Table 6: Oxidation Reactions ...................................................................................................................... 16
Table 7: CO2 Emissions ............................................................................................................................... 16
Table 8: Biofuel Exemptions ....................................................................................................................... 18
Table 9: Glycerine Economics .................................................................................................................... 18
Table 10: Fee Summary ............................................................................................................................... 19
Table 11: Rankine Cycle Cost Report .......................................................................................................... 20
Table 12: Cost Benefits ............................................................................................................................... 21
Table 13: Babington Economics .................................................................................................................. 25
viii
Nomenclature
BPF Biodiesel Processing Facility
GHG Greenhouse Gases
MMG Million Gallons Annually
TBD To Be Determined
AHU Air Handling Unit
HRU Heat Recovery Unit
NOx Nitrogen Oxides
PGy Propylene Glycol
EAW Equivalent Annual Worth
CO2 Carbon Dioxide
1
1.0 Introduction
1.1 Background
Biodiesel is a type of non-petroleum based diesel fuel made from raw/waste vegetable oils. Its
use in diesel engines has become popular due to its lubricity and its renewability as an energy resource.
Biodiesel is typically produced at BPF where conversion of waste vegetable oils or seed oils into high
grade diesel occurs. These plants all employ the use of catalysts to accelerate conversion of the raw oils
into usable oils. What remains common to all these processes is the waste type, a by-product of
transesterfication called glycerine.
The process of manufacturing biodiesel commonly involves the use of a methanol, vegetable oil
and catalysts with a mix of process gas/electrical heat, depending on the process type. To varying
degrees, biodiesel plants generate 1-3 units of glycerine per 10 units of biodiesel produced[3]. A plant
generating 100MMG of biodiesel will produce anywhere from 10-30MMG of glycerine. This represents
an unacceptably high level of waste for BDF and to date remains unsolved. It is the focus of this study to
utilize that waste in a way which improves the efficiency of BDF and improve economics while reducing
greenhouse gas emissions. This includes the design of improved glycerine burners and the addition of a
steam condensing turbine.
1.2 Concept
The objective of this paper is to develop a conceptual model for a utility on how to burn
glycerine in a way that increases plant utilization while resolving waste issues. The model that will be
2
discussed in the following pages will walk the reader through the concept of oxidizing glycerine and see
how that concept compliments current plant operations.
The model parameters were chosen based upon facilities currently being constructed in
Manitoba, Canada. These parameters include physical plant characteristics such as process heat and
electrical requirements, others include climatic conditions local to the climate which will impact how
that facility operates. For this project a 60MMG biodiesel plant was chosen for the study with the ability
of scaling incorporated into it.
1.3 Scope of work
The scope of work is limited to the plant itself, it will not include energy balances for feed stocks
or debate the viability of the fuel as this has been argued to varying degrees of success. The project will
focus on:
a) Combustibility and Burner design
b) Steam generation for process heat and Thermodynamic Cycles
c) Steam generation for electricity
d) Environmental Impact
e) Economics
3
2.0 Combustibility and Burner design
2.1 Fuel Characteristics
Glycerine is not a common fuel for combustion purposes, so the design of the burner must
facilitate any unique aspects of the fuels chemical properties. The conditions used for proper
combustion have been approximated to match glycerine to #6 Bunker oil at 30⁰C. Referring to figure 1
this requires heating the glycerine to approximately 60⁰C to achieve a similar viscosity to that of Bunker
Oil. After heating the glycerine, it will be atomized with steam and oxidized with air. The fuel velocity
rates have been determined at around 40 m/s – based on similar size oil burners and the higher heating
value (HHV) of glycerine.
Figure 1: Viscosity of Glycerine
A fuel comparison can be seen in table 2 which lists the chemical properties for Glycerine and No. 6
Bunker Oil. The key points in this table are the viscosity, which show a similar correlation at 60⁰C. More
importantly this table shows that the fuel comparison is valid, and will justify assumptions later on.
0
2000
4000
6000
8000
10000
12000
14000
0 50 100 150
Ce
nti
po
ise
s/m
Pa
s
Temperature ºC
Temperature vs Viscosity
80%
85%
90%
95%
100%
Concentration
2.2 Babington Burner
A Babington burner is a type of fuel burner which capitalizes on highl
degree of contaminants. A figure of a typical Babington burner (in Figure
of the atomization component of the burner.
4
Table 1: Fuel Comparisons
A Babington burner is a type of fuel burner which capitalizes on highly viscous fuels with a high
A figure of a typical Babington burner (in Figure 2) shows a cross sectional area
of the atomization component of the burner.
y viscous fuels with a high
) shows a cross sectional area
5
Figure 2: Airtronic Babington Burner
The principle behind this burner is simple atomization of a viscous fuel. Fuel is poured over the
sphere and a thin film of fuel forms over the atomizer hole. Compressed air is shot into the hollow
sphere and atomizes the fuel as it passes over the atomizer air slot. What makes this burner unique is
that fuel is not mechanically atomized as is the case with other burners. The surface tension of the fuel
causes shearing when it passes over the atomizer air slot. This results very tiny droplets of fuel,
increasing the available surface area and providing a better combustion.
Figure 3 shows a preliminary design for a Babington burner. The excel file assumes that the fuel
atomization rate must equal the desired flow rate for developing the desired amount of steam. In this
case the desired flow rate through the burner was 1.418kg/s. The red box indicates the number of
burners that would have to be installed for this flow rate (240,000). This of course exceeds practicality
from an economic and engineering perspective, but is still valuable in the context of the facility size.
Although the scope of this study is based on a 60MMG plant, it is easy to see how this burner could be
retrofitted for smaller plants that aren’t utilizing steam generation. Another practical concern for this
burner is the fuel turn down rate. Because process loads will vary throughout the course of operation, it
will be important to moderate flow rates in an effort to match demand. This burner is highly dependent
6
on tangential fuel velocity; if the velocity is too low, the fuel will stagnate on the ball surface and trickle
away from the atomization hole. If the velocity is too high, the fuel will separate from the ball or splash
off, becoming unstable and unpredictable.
Figure 3: Babington Program
2.2.1 Process Heating only
The Babington does not meet fuel rates required for small boiler systems, but it does supply
enough heat for process heat applications. Table 2 shows the number of burners and atomizers that
are required per burner. These calculations were used with a similar program as in figure 4, it makes the
assumption that the transfer of thermal energy to a load source would absorb 65% of the total fuel
burned. Although the number of burners is high, the important part to understand is that the process
7
heating requirement won’t be localized but used on over 12 appliances so in this case it would be 9
burners per application.
Process heating 2500kW
Required Fuel Rate 0.1747 kg/s
# of Burners 105
# of Atomizers 15
Surface Area 1.9m2 Table 2: Process Heat only
2.3 Oil Burners for Electrical Generation
Ultimately the selection of a burner will be dependent on proven technology that is currently in
use. Since the fuel properties of glycerine closely match those of bunker oil, the burner chosen for this
application is an oil burner. These burners (shown in Appendix A) offer the flexibility of high and low fuel
rates, but are also designed for optimal fuel atomization and low NOx output. The fuel rates required for
this burner are summarized in table 2. The suggested literature for turndown rates on this type of
burner is not to exceed 50% of the design flow rate [10].
Operation Fuel Flow Rate [kg/s] % Reduction from ideal
Design Conditions 1.4184 0%
Max operation 2.3641 40.0%
Minimum Operation 0.7881 44.4%
Reserves (1day outage) 1.4184 0%
Reserves (5day outage) 0.28371 79.9%
Table 3: Burner Fuel Rates
1 This exceeds allowable turndown rates, increased storage is necessary which may not be economical
8
2.4 Boilers
For steam generation, wall tube boilers are currently the technology of choice for burning oils.
Although this study does not undergo a quantitative analysis of wall tube boilers, a schematic of one is
show in figure 4 below. The fuel is atomized through low NOx burners in the lower portion of the boiler,
overfire airports inject more air so that temperatures are maintained and NOx is minimized (NOx
develops at temperatures in excess of 1000⁰C). The superheaters, primary and secondary coils are
located respectively at the top of the burner. The selection of a boiler will be critical to the economics of
the proposed cycle and will discussed in more detail in section 6.0
Figure 4: Wall Tube Boiler
9
3.0 Steam generation for process heat and Thermodynamic Cycles
3.1 Modeling the Rankine Cycle
Depending on the size of the plant and the water content of the feedstock, BDF generally
consume large amounts of energy. Specifically the electrical demands and the natural gas supply.
Because the waste can be considered an abundant fuel supply which can provide both of these demands,
the rankine cycle was chosen because of its commonality and flexibility. The rankine cycle is extremely
common for energy generation and particularly efficient for small commercial operations which utilize
cogeneration.
Figure 5 shows the proposed rankine cycle which incorporates a high and low pressure turbine
section. The model section (shown in Appendix B with BDF model) calculates all of the different flow
rates, temperatures and pressures based on the assumption of steady state conditions, which for this
application is a reasonable assumption
because the mass influx of fuel is assumed to
equal the burner flow rate, internal energy
differences can be kept to a minimum.
The model was calibrated using actual
process heating and electrical loads provided
by a commercial supplier for turnkey BDF;
because many inputs were not known, the
model used inputs from equipment of a similar size and operation [10],[11]. The important
characteristics of this cycle are shown in table 4.
Rankine Cycle Model
Process Heating Load 3.251MW
Electrical Heating Load 1.8MW
Turbine Work output (w/ losses) 10.798 MW
Condensor heat loss 3.932 kW
Glycerine yield (14.4%) - Annually 8,640,000 gal
Burner output 24.255 MW
Table 4: Model Properties
3.2 AHU Supplemental Heating
Manitoba climates are particularly harsh and cold. The temperature
can approach 60⁰C (140⁰F), this requires that building systems be designed to maximum (or extreme)
weather conditions. The cycle proposed above,
perspective but quite poor with respect to the first law
10
Figure 5: Rankine Cycle
3.2 AHU Supplemental Heating
climates are particularly harsh and cold. The temperature difference
⁰C (140⁰F), this requires that building systems be designed to maximum (or extreme)
weather conditions. The cycle proposed above, is considered to be efficient from an engineering
perspective but quite poor with respect to the first law of thermodynamics. The losses from the
difference between seasons
⁰C (140⁰F), this requires that building systems be designed to maximum (or extreme)
cient from an engineering
. The losses from the
11
condenser in this case can be used as a supplemental heat source for the building during the winter
months.
A typical industrial building was modeled (see Appendix C) by using Trace 700 load design
software – a commercially available software used for designing air handling and ventilation systems.
The Results of this analysis can be seen in appendix C and
summarized in table 3; the important aspect of the
analysis is the peak load for the AHU. This load can be seen
as 2350MBh (688kW) which is the highest consumption of
energy on the coldest day of the year. The benefits can
be readily seen when we look at using the waste heat from
the condenser to heat the building. Typical AHU coils see a
180⁰F – 159⁰F temperature drop; in this case the
condenser coils drop at 250⁰F (partially condensed) - 248⁰F
(fully condensed), which means on the coldest day of
winter the condenser will be forced to waste heat to the
atmosphere [7]. The condenser supplies 3932kW of thermal heat, while the AHU only requires 688kW
showing an abundance of 3244kW. Using the inlet and exit temperatures of the condenser coils as the
new temperature conditions for the Trace simulation a new analysis was done (see appendix C), these
results are summarized in Table 4.
The results indicate a lower airflow rate for the same AHU which translates into lower operating
costs for the unit, the AHU would be scaled down significantly due to this decrease in airflow2.
2 Minimum ventilation rates must still be met
Building Simulation – Standard
Area 50000ft2
Airflow – Ventilation 5137 CFM
Peak Building Load 688kW
Entering Air Temp. -27⁰F
Leaving Air Temp. 102.7⁰F
Table 4: Condenser Temps matched to coil
Table 3: Standard Coil Simulation Results
Building Simulation – Coil Mod.
Area 50000ft2
Airflow – Ventilation 1345.7 CFM
Peak Building Load 688kW
Entering Air Temp. -27⁰F
Leaving Air Temp. 102.7⁰F
12
4.0 Steam Generation for Electricity
4.1 Rankine Cycle optimization
Defining the input and output parameters of the model is difficult, simply because of the
economics and the output of the turbine. Smaller steam turbines are used to a lesser extent because of
the large capital investment to output ratio. On the opposite spectrum, large turbines may have a
better economic:output ratio but be prohibitively expensive due to the large initial capital investment.
The driving factor behind this particular model was the glycerine burned:electrical output ratio. Table 5,
shows the potential economic benefits of burning different quantities of glycerine. The economics of
this is defined later in section 6.3, but it is worthwhile to discuss here. The electrical capacity has huge
variation with respect to the glycerine capacity. With every doubling of fuel capacity the electrical
output increases by 25-60%. This particular cycle has a capital investment of nearly 50M dollars, and the
only profit is the electrical output. For this reason the input steam conditions were modeled from the
perspective of the required amount of work. Although the enthalpy is known for the input steam
conditions and the process loads, the low pressure steam at state 6 (figure 5) is not known, similarly the
work output is unknown. The model was calibrated by choosing a maximum amount of work and then
determining a realistic enthalpy value for the low pressure saturated steam. Of course this begs the
question about what type of turbine is being used. Some turbines are designed to be fully condensing
while other function only with superheated steam exiting the low pressure side. It was assumed here
that a medium could be found that would satisfy this low pressure steam. For this situation the quality
was 0.2 – between a fully condensing and superheated type turbine.
13
Glycerine Capacity
Annually [MMG]
Electrical Capacity
[MW]
$ Value (@ 0.06$/kWh)
6 6.399 3,040,804
12 16.397 7,791,854
18 26.395 12,542,904
24 36.393 17,293,953
30 46.391 22,045,003
Table 5: Glycerine Capacity
14
5.0 Environmental Impact
5.1 Photosynthesis and Sequestered Carbon
Biodiesel has gained recent notoriety in North
America due to its renewability as a fuel source. In the
context of this study, renewability plays an important part
with respect to green house gas emissions. It is customary
to think of burning fuels as a way of contributing to green
house gases, but the underlying philosophy about how we
think of green house gas needs to be restructured.
When we refer to green house gas emissions we are referring
to burning fossil fuels (in general), fuels that cannot be retrieved in the near future, and release
substantial quantities of CO2, Nitrous oxides, Sulfer oxides and particulate into the atmosphere. The
renewability movement or ‘green sector’ (now commonplace in most engineering sectors) defines
renewable fuels as fuels which can be recreated in a relatively short period of time and are generally
derived through the earth’s natural resources.
Biodiesel has achieved this classification because it is derived from plant matter, which
harnesses wind and light energy to make a fuel in a relatively short
period of time.
Plants harness wind energy by strengthening root and stem
systems that help deliver nutrients for growth, and harness light energy
through photosynthesis. Photosynthesis (figure 7) is particularly
important to understanding why burning glycerine will have a net zero
Figure 6: Photosynthesis Cycle [17]
Figure 7: Carbon Cycle [18]
15
green house gas emission status. Plants use light energy to synthesize carbon dioxide and water to form
plant sugars [16]. The carbon dioxide that the plant harnesses from the air can be thought of as
sequestering it, or storing it in the plant. If for example we chose to burn the sunflower in figure 6, it
would release the same amount of carbon dioxide into the air as it had initially sequestered during its
growth.
This can be extended to the concept of burning glycerine. Because glycerine is a direct derivative
of triglycerides (which are formed during the plants growth) the glycerine is said to be storing the CO2
that it had initially used for growing. So when we burn glycerine although we are releasing CO2 into the
air, we are simply replacing the CO2 that was taken from the air during the plants growth.
5.2 Carbon Dioxide Emissions
The emissions produced from burning glycerine were compared to the natural gas consumption
to determine if burning glycerine is better or worse in terms of how much CO2 into the air. Cleary, as
discussed in section 5.1, no matter how much glycerine we burn, as long as it’s coming from a plant
source the net difference is zero. Table 6 shows the theoretical stoichiometric calculations for the
combustion of several different fuels including glycerine. Many fuels, particularly coal contain trace
amounts of sulphur which can lead to different results. For these calculations, sulphur content is non
existant, and nitrous oxides represent less than 10% of the total waste emissions so using pure oxygen
as the oxidant is a reasonable approximation [10].
Although Glycerine does not have any sulphur content it should be noted that when glycerine is
heated to 280⁰C it forms a gas refered to as Acrolein (C3H40). Acrolein is a pulmonary irritant and has
been used as a chemical weapon in warfare. However for combustion temperatures in excess of 500⁰C
16
there is no risk of this gas developing and these temperatures are regularly achieved in industrial
boilers.[4].
Table 6: Oxidation Reactions
The CO2 emissions per kg/fuel were calculated for a 1 year period. Table 7 shows the total
metric tons of CO2 emitted into the atmosphere from 1 year of operating a biodiesel plant. Although
some of these fuels aren’t used for this application they are shown for comparison purposes. Notably
glycerine has the highest quantity of fuel burned per year with the lowest amount of CO2 emissions. For
this application, glycerine emits 52% less CO2 then natural gas, and 100% better when we evaluate the
net emissions into the atmosphere.
Annual Emissions
Fuel Fuel Quantity [kg] CO2 Emissions [Tons] Natural Gas 14,713,422 40,358
Glycerine 40,442,554 19,331
Ethanol 25,744,916 49,198
Coal 32,059,768 79,508
Diesel 16,512,130 52,211 Table 7: CO2 Emissions
17
6.0 Economics
6.1 Biodiesel Economics
Biodiesel has been one of the fastest growing fuels in this decade, climbing by nearly 50%
between 2002-2007. Nearly 50% of all the biodiesel consumed globally is in Europe and only in the past
2 years has the North American market started to take part (figure 8).
Figure 8: Biodiesel Distribution Worldwide [14]
The economics behind BDF’s are to a certain degree the most important aspect to consider
before building one. The problem with defining the economics of these plants is the inability to predict
market demand, market value; combine that with fluctuating supplies and construction costs, it is
considered by many to be a risky purchase. Biodiesel typically costs about 90 to 150cents per litre
depending on quality of feedstock and the market value. Since it is not a competitive fuel, governments
are attempting to stimulate the market by offering tax exemptions in an effort to meet projected
biodiesel/diesel mixes; in Canada the Goal is 2% renewable fuel content in diesel by 2010. The
Canadian plan (table 8) has been to subsidize biofuels with a payment plan for 8 yrs in an effort to help
BDF’s get off the ground and diminish the market’s volatility [13].
18
Table 8: Biofuel Exemptions [13]
6.2 Glycerine Economics
The market value for glycerine is extremely low relative to its potential thermal energy. With
global production of biodiesel doubling almost every 5 years, the market for glycerine has saturated and
dropped by 45% from its steadfast price from the late 70’s to the early 2000’s [15]. Although there are
many uses for glycerine, surprisingly it has not yet been widely excepted as a potential fuel. Table 9
gives a brief cost breakdown of the sale prices on glycerine. The highest value peaks out at 25 cents a
kilogram; the theoretical electrical value is nearly 2 orders of magnitude higher which indicate a strong
potential for electrical generation.
Glycerine Market Value
HHV 19,000 kJ/kg
High Grade Glycerine market value 0.25$/kg
Low Grade Glycerine market value 0.14$/kg
Thermal Energy per unit mass-time 19,000kW
Theoretical Electrical Energy derived η=30% 5700kW
Electrical market value @ 0.06$/kWh 342$/kg Table 9: Glycerine Economics [15]
6.3 Plant expansion
There are a number of different ways to define the feasibility for of the proposed cycle above.
Two different schemes have been developed (section 6.4) in an effort to demonstrate the cost
19
effectiveness of the cycle. Because of the scale and proposed cost of this project, it is difficult to develop
accurate numbers; initial cost estimates are usually based on years of experience, and final cost
estimates (if ever possible) will only be decided when the contractors in their own area of expertise have
had time to decide what it will cost them. The following cost estimate (Table 11) was developed from
well known labour rates (Table 10), and less than well known equipment costs, it could therefore be
grouped into a class D cost report – (representing substantial tolerances in equipment from vendors).
FEE SCHEDULE
Plumber/welder/pipe fitter 65$/hr
Steam Fitters/Masons 85$/hr
Millwrights 75$/hr
Electrician 65$/hr
Barrister 200$/hr
General Labour 40$/hr
Junior/Senior Engineer 100/180$/hr
Drafting 75$/hr
Drawings 2000$/per
Administrative 30$/hr
Table 10: Fee Summary
20
Table 11: Rankine Cycle Cost Report
21
The annual utility costs for the 60MMG plant were determined based on 2008 gas and electrical
prices from Manitoba Hydro [9]. By adding the proposed rankine cycle, the cost budgeting becomes
more complicated due to the fact that the utility is now selling electricity as opposed to consuming it.
In Manitoba, generating electricity is prohibited in part because Manitoba hydro has a
dominating control on the market. This is not to say that it cannot be done, but for the purpose of this
study, it was assumed that Manitoba hydro would take 33% off of the sale price per kWh – about
0.02$/kWh. The annual utility costs comparing the current plant and the proposed expansion are shown
in table 12. The table also takes into account for plant outages which would force the plant to draw
power from the grid for continued production.
Table 12: Cost Benefits
22
6.4 Plant Case Studies
A five, ten and 30 year cost study was done to determine the equivalent annual costs of
purchasing a 60MMG plant and a 60MMG plant with a rankine cycle incorporated into it. The EAC was
chosen as the index to measure the ‘quality’ of the purchase by annualizing the capital investments with
the net profit and annual utility rates. The goal of the EAC comparison is to compare two options and
the option with the highest EAC is defined as being the better option – within the confines of that index.
The resulting graphs can be seen in figures 9, 10 and 11, showing the gallons of glycerine burned
on the x-axis and the EAC on the y-axis. The two options plotted were the standard 60MMG plant and
the proposed glycerine burning plant. The rates of glycerine produced were varied, because the
glycerine plant is economically dependent on the amount of glycerine produced. The breakeven point, ie
where both options are equally good options occur when glycerine production levels far exceed the
capacity of the 60MMG plant. The 5 year EAC study shows that the required glycerine for production
exceeds the amount of biodiesel produced for that plant. This should not be surprising to the reader
when we understand that over 100 million dollars is trying to be paid back in a 5 year period, - nothing
short of ridiculous.
The 10 year EAC study has a breakeven point of about 35 million gallons of glycerine produced,
nearly 3x of the maximum glycerine production capacity. Finally a 30 year study was done which
showed the glycerine plant to be the better choice. The three graphs all show the same principle; that
the glycerine plant is in principle the better choice because of it’s incrementally higher annual sales in
electricity. The glycerine plant may not be reasonable however, when we evaluate the capital costs.
23
Figure 9: 5 year EAC study
Figure 10: 10 year EAC study
-20,000,000
-15,000,000
-10,000,000
-5,000,000
0
5,000,000
0 20 40 60 80
do
lla
rs [
$]C
DN
glycerine production [million gallon]
5 year EAC
60MMG Plant
Glycerine Plant
-6,000,000
-4,000,000
-2,000,000
0
2,000,000
4,000,000
6,000,000
8,000,000
10,000,000
12,000,000
14,000,000
0 20 40 60 80
do
lla
rs [
$]
CD
N
Glycerine Production [million gal]
10 year EAC
60MMG Plant
Glycerine Plant
24
Figure 11: 30 year EAC study
6.5 Babington Burner Economics
The only known manufacturer for Babington burners is Babington Technology, which design
military grade Babington burner equipment. Babington Technology refused to offer a purchase quote,
but did supply heating outputs for their units [19]. Since no cost was available it was assumed that each
unit had a purchase price of $10,000, and that the burner could easily burn glycerine (table 13). Since
the glycerine is considered a waste stream for the BDF, no assigned value was attached to it. This results
in the company recovering it’s capital investment in about half a year and eliminates 32% of the waste
stream (glycerine).
0
2,000,000
4,000,000
6,000,000
8,000,000
10,000,000
12,000,000
14,000,000
16,000,000
0 10 20 30 40 50
Do
lla
rs [
$]
CD
N
Glycerine produced [million gallon
30 year EAC
60MMG Plant
Glycerine Plant
25
Babington PMB - heat output 80,000Btu/hr
Process Heating Requirements 8.54MMBtu/hr
# of Burners Required 107
Assumed Cost per unit $10,000.00
Total Cost of burners $1,067,500.00
Natural Gas Cost (annually) $2,578,141.00
Payback Period 151 days
Table 13: Babington Economics
26
7.0 Discussion
7.1 General Discussion
The goal of this study was to come up with a way of completing the plant cycle and having a BDF
completely self sustained, independent of both the electrical grid and gas lines. For electrical generation
we need the rankine cycle, and heat can be derived by electricity or burning of fuels. So why is the cost
of sustainability so high then? From a control volume perspective the system makes perfect sense. Raw
goods enter the plant and finished product leaves, in the middle we have unused product (glycerine)
driving all the internal needs of the plant. The high costs are more directly related to the goal of the
project; that is maximizing output for two products when the principles of the plant were designed
around one product. From a business model perspective the glycerine plant should be looked at as a
separate entity from the BDF. If we want to turn glycerine into electricity, then it should be separate
from the biodiesel plant in that the BDF isn’t trying to recuperate operating costs from the rankine cycle
by subsidizing it with profits from selling biodiesel. Instead the glycerine plant should be geographically
located so that it can be the dumping ground for several BDF’s and in turn optimize a cycle which is
designed around maximizing fuel rates and ultimately electricity.
7.2 Errors
The biggest source of error is due to the compounding errors associated with assumptions.
Assumptions by their nature are suppositions which come from experience and an ability to predict a
situation based upon various parameters. For example suppose that certain turbine efficiencies were
assumed to high. The affect is higher turbine output and corresponding cost associated with a larger
capacity turbine.
27
Another source of error lies in the assumption of linearity ie steady state conditions for the
rankine cycle. Modeling this as a transient system is beyond the scope of this project for a number of
reasons. First, an intimate knowledge of the exact equipment would be necessary to really apply the
proper conditions for each component. The second problem lies in modeling the boiler and the burner
technology – which do not exist. For proper burner output, a CFD model would have to be completed in
order better understand how the combustibles will behave. Lastly, there is no available data on
combustion of glycerine. Every fuel will have a specific burning characteristic and this will affect fuel/air
ratios and also burner placement in the boiler.
Product info is another source of error which is unfortunately due to nature of the products, and
the information being requested. The general trend among manufacturers, particularly large industrial
equipment is to not give pricing without drawings and project data. This amounts to assumptions for
pricing on equipment, many of which were taken from similar used units on sale from private sellers.
28
8.0 Conclusion
When we look at the economics of trying to turn glycerine into a product (ie electricity), we can
see that it is expensive and uneconomical for a plant only producing 60MMG of biodiesel. It can be
made viable by increasing fuel rates, but doing this changes the dynamics of the model and doesn’t
account for any benefits that may be realized by scaling. The 30 year EAC study made practical sense but
lacks long term potential. Hydro generating stations for example may only make a profit after 20 years
of operation, but it is assumed the station will operate for 50 years. We cannot make any assumptions
about the proposed rankine cycle, and although there may be some residual sale value in the system at
the end of the study life it is quite likely that the equipment would be exhausted at the end of that time.
The results of this study indicate a clear correlation between fuel viability and economics. There
can be no question about whether glycerine is a good fuel. Is scores low on overall green house gas
emissions, and from the utility in the business of making biodiesel, it is essentially free. For anyone not
in the biodiesel business, it would make little economic sense to purchase it as a combustible fuel source.
The fuel has a low energy density when compared to fuels like natural gas or diesel, so its fuel benefits
can only be realized in the special case where it is generated with little expense.
29
References
[1] Martin Tampier and Doug Smith and Eric Bibeau Paul Beauchemin, Identifying Environmentally
Preferable Uses for Biomass Resources, Vancouver, B.C.: 2004
[2] C.C. Heald, Cameron Hydraulic Data, 19th Ed., Canada: Flowserve, 2002.
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[Sept 18, 2008].
[4] Jan F. Stevens and Claudia S. Maier, “Acrolein: Sources, metabolism, and biomolecular interactions
relevant to human health and disease” ,Oregon State University, Corvallis, OR. 52, 2008.
[5] James A. Kenar, “Glycerine: Sweet Alternatives”, US Department of Agriculture, Peoria, IL. Vol 19
#11, 2007.
[6] Richard Sonntag and Claus Borgnakke and Gordon Van Wylen, Fundamentals of Thermodynamics,
6th Ed,.Danvers,MA: John Wiley & Sons, 2003.
[7] ASHRAE Fundamentals Handbook, 2001 Ed, Illinois: ASHRAE, 2001.
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heat and mass transfer, 6th Ed., Danvers, MA: John Wiley & Sons,2007.
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http://www.hydro.mb.ca/regulatory_affairs/energy_rates/natural_gas/current_rates.shtml [Oct
16, 2008].
[10] Steven C. Stultz and John B. Kitto, Steam it’s generation and use,4th Ed.,Ohio,
U.S.A.:Mcdermot,1992.
30
[11] Manturbo. “Steam Turbines” [online]. Available:
http://www.manturbo.com/en/500/500_productdetail.php?prod=&cid=180 [Nov 2, 2008].
[12] James Riggs and David Bedworth and Sabah Randhawa and Ata Khan, Engineering Economics,2nd
Ed,. Canada: McGraw-Hill Companies, 1997.
[13] Natural Resources Canada. “Biofuel Incentives” [online]. Available:
http://oee.nrcan.gc.ca/transportation/ecoenergy-biofuels/incentive.cfm?attr=16 [Nov 17, 2008].
[14] SRI Consulting. “Biodiesel” [online]. Available:
http://www.sriconsulting.com/CEH/Public/Reports/205.0000/ [Oct 18, 2008].
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2008]
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synthesis.html&usg=__RGR_6x28vsFCrqND4WGxJGflo=&h=357&w=400&sz=52&hl=en&start=2&t
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31
Appendix A
A typical Oil Burner used in large scale boilers
32
Appendix B
The following Calculations were performed using Microsoft Excel and were derived from [6],[10]
33
34
This is the assumed model for the biodiesel model for which the rankine cycle was modeled after.
35
Appendix C
Building Justification and Design
Assumption Justification
Area 100x500ft Standard
Building height 35ft Standard (must accommodate boiler)
No ventilation plenum space Not concerned with ventilation losses
Slab Construction 8” HW Conrete Standard
Roof – 4” insulation Steel sheet R-20 90⁰ pitch Standard
0.1Btuh/ft2 – internal building load Based off of machinery losses
Building Occupants – 25 ASHRAE suggested
0.5 W/ft2 – lighting Internal load from lighting
Infiltration – 0.6 Air Changes /hr Based on average construction quality
Wall Construction – Gyp – Steel Frame 6” ins
No Shading, walls @ 10⁰, 100⁰, 190⁰ 280⁰ from sun
Typical
Slab Construction – on grade per. Losses Standard
ASHRAE 61.1 Area Ventilation Standard
Heat – Ventilation and Space reheat Typical
Windows 2% of floor space
w/ Tpl Low-e Film (44) 6mm Air
Typical
Thermostat Dry bulb set point 20⁰C
±10% drift point
Typical
Operating AHU schedule – manufacturing type Typical to plant operation
36
The following simulation was done using trace 700. This simulation models the facility with a standard
heating coil with the temperature drop of the glycol loop @ 180F⁰ – 159⁰F
37
This model demonstrates the decreased CFM required in the AHU when the coils are changed to match
the condenser temperature drops of 248⁰F - 250⁰F
